The ocean is now the hottest ever recorded by humans, not only at the surface, but also in the upper 2000 meters.
Yesterday the news came out that 2024 the hottest year ever recorded has become. And that was noticeable worldwide. In the past 12 months, no fewer than 104 countries recorded their highest temperatures ever. Droughts, heat waves, floods and forest fires have left their mark, from Africa and South Asia to the Philippines, Brazil, Europe, the United States and Chile. But not only land temperatures are rising rapidly, the oceans are also warming further. In fact, in 2024, sea water temperatures also broke all records.
Record year
Three international teams worked together on this research and came to the same conclusion: the ocean is warming and 2024 is a new record year. And that is not the first time. Ocean warming is an ongoing trend, with new records being set every year. “Previous records for ocean temperatures continue to be surpassed,” said researcher Lijing Cheng Institute of Atmospheric Physics at the Chinese Academy of Sciences.
Up to 2000 meters
The image below shows the ocean heat content (OHC) up to 2000 meters. Blue and red colors indicate whether a given year was colder or warmer than the reference period 1981-2010. Scientists use this period as a basis for their comparison. The key point is that values continue to rise year after year.
Between 2023 and 2024, the OHC in the upper 2000 meters increased by as much as 16 zettajoules (1021 Joules), which is about 140 times the world’s total electricity production in 2023. “Ocean heat content has increased steadily by 15 to 20 zettajoules over the past five years, despite the influences of La Niña and El Niño,” said researcher Michael Mann of the University of Pennsylvania.
Surface water
The temperature of the surface water is also breaking records. This temperature concerns the water at the surface, where the ocean comes into contact with the atmosphere. Surface temperatures are important because they determine how quickly heat and moisture (humidity) can transfer from the ocean to the air, which affects the weather. The increase in surface temperatures since the late 1950s is staggering.
Regional differences
The changes are not the same everywhere; there are significant regional differences. For example, the Atlantic, Mediterranean, and Southern Oceans warm around midlatitudes. But while some parts of the North Pacific warmed rapidly in 2024, other areas (such as the tropics) lagged behind. This is mainly due to the influence of La Niña and El Niño. Heat has even built up at both the North and South Poles.
Ocean is crucial
The findings are worrying. The ocean plays a key role in the Earth’s climate – as much as 90 percent of the excess heat from global warming is stored in the ocean, which covers 70 percent of the Earth’s surface. As a result, the ocean controls our weather patterns by bringing heat and moisture to the atmosphere. Moreover, the ocean determines how quickly climate change continues. “If you want to understand what’s happening to the climate, look at the ocean,” notes study co-author John Abraham.
Climate
The ocean influences the climate mainly by increasing water vapor in the atmosphere, which amplifies the extremes in the hydrological cycle. “Water vapor is also a powerful greenhouse gas,” explains researcher Kevin Trenberth, a senior scientist at the National Center for Atmospheric Researchout. “The additional warming also causes desiccation, which increases the risk of drought and forest fires. At the same time, it also fuels storms of all kinds, increasing the risk of flooding. This includes hurricanes and typhoons.”
In summary, the study shows that rising ocean temperatures are an undeniable trend worldwide. The consequences for ecosystems, weather patterns and human societies are already clearly visible, ranging from extreme heat waves and droughts to an increased risk of floods and storms. “The ocean is like a global warming alarm because it stores most of the excess heat that enters the climate system from human emissions,” says Karina von Schuckmann of Mercator Ocean Internationalco-author of the study. “If we do not take action to slow climate change, the disruptions, unprecedented changes and impacts, costs and damage will only continue to increase.”
